It's always been this way on Sandy Bridge. More vram means better textures, that's about it. It doesn't really seem to boost performance best I can tell reading up on it a couple months ago.
Also it will also use more system memory as video memory if it needs it.
Since the integrated graphics reserve some system ram, if you add ram the card will make use of the larger ram available to it and allocate more to the graphics. It's a default behavior